225 fuel burn and cruise

[fishnfetch]

thanks ferm. thats about what i figured. im having some trouble (ran out of gas yesterday in the harbor) adjusting to the small fuel tank size. right now i dont have the scratch to put a fuel flow meter in it to really dial in my best cruise economy. i will be asking santa for one though. lol. im spinning a 14 1/2x17 aluminum prop, i may try and tinker with that as well but i need to be able to measure fuel flow before i do

[bgreene]

Old fashioned method:
1. Fill the tank full.
2. Go for a measured boat ride at a given rpm- say 10 miles round trip.
3. Then re fill tank and see how many gallons it takes.

Then you'll know for sure, absolute.

The older 225 loopers gulp fuel when you put the hammer down.
If running under 4,000 rpm shouldnt be too bad. If run hard...... I'd guess 20_+ gallons per hr no problem.

[THEFERMANATOR]

Originally Posted by bgreene

Old fashioned method:
1. Fill the tank full.
2. Go for a measured boat ride at a given rpm- say 10 miles round trip.
3. Then re fill tank and see how many gallons it takes.

Then you'll know for sure, absolute.

The older 225 loopers gulp fuel when you put the hammer down.
If running under 4,000 rpm shouldnt be too bad. If run hard...... I'd guess 20_+ gallons per hr no problem.

Depends upon the year. The 86-87 engines were the best on fuel of the big loopers as they were a 2.7L engine with very aggressive porting. The 88-91 engines were the best all around with the 3.0L displacement, milder porting and idle reliefs which made them idle better and more reliable. The 93+ engines have the smallest ports and very restrictive exhaust in them. It makes for good off idle performance along with cleaner emissions. they had to add in finger ports though to get the HP back that was lost with the exhaust changes and also added in a higher flow tuner. Then around 99 or so they offerred the 250 which is a 225 with better porting i nthe exhaust I believe and the early style intake. The 93+ engines are by far the thirstiest of the big OMC loopers though due to the restrictive exhaust and the need for finger ports to compensate.

A stock 225 should burn around 23-25 GPH at WOT, and fuel burn drastically changes around 4,000RPM's. I know my ported and max bored 225 would gulp down an easy 28-29 GPH when I dropped the hammer on it, but burned 11 GPH runnign along at 3600-3700 and about 12.5GPH at 4000RPM's. It actually burned more at 3400 than it did at 3600 though, and this is where a fuel flow meter is worth it's weight in gold.

[phester]

Originally Posted by THEFERMANATOR

Depends upon the year. The 86-87 engines were the best on fuel of the big loopers as they were a 2.7L engine with very aggressive porting. The 88-91 engines were the best all around with the 3.0L displacement, milder porting and idle reliefs which made them idle better and more reliable. The 93+ engines have the smallest ports and very restrictive exhaust in them. It makes for good off idle performance along with cleaner emissions. they had to add in finger ports though to get the HP back that was lost with the exhaust changes and also added in a higher flow tuner. Then around 99 or so they offerred the 250 which is a 225 with better porting i nthe exhaust I believe and the early style intake. The 93+ engines are by far the thirstiest of the big OMC loopers though due to the restrictive exhaust and the need for finger ports to compensate.

A stock 225 should burn around 23-25 GPH at WOT, and fuel burn drastically changes around 4,000RPM's. I know my ported and max bored 225 would gulp down an easy 28-29 GPH when I dropped the hammer on it, but burned 11 GPH runnign along at 3600-3700 and about 12.5GPH at 4000RPM's. It actually burned more at 3400 than it did at 3600 though, and this is where a fuel flow meter is worth it's weight in gold.

Ferm, you really know your omc's....just like Skools....I've got a similar question. You mention 88-91 engines, as well as 1993 and beyond.... any input about a 1992 60* looper 150 johnson. It has been a very reliable engine and it moves out my V pretty good. I just wanted your input on that particular year....and I've asked this before but never got a difinitive answer....the stock factory decals on the hood say Johnson 150 "silver star series." Any idea what S.S.S. means?

[THEFERMANATOR]

Originally Posted by phester

Ferm, you really know your omc's....just like Skools....I've got a similar question. You mention 88-91 engines, as well as 1993 and beyond.... any input about a 1992 60* looper 150 johnson. It has been a very reliable engine and it moves out my V pretty good. I just wanted your input on that particular year....and I've asked this before but never got a difinitive answer....the stock factory decals on the hood say Johnson 150 "silver star series." Any idea what S.S.S. means?

The silver star series I believe was just a bass boat designation, pretty much just decals. The 60 degree looper engines are argueably the best outboard that OMC EVER built. They are a bit thirstier than an equivelant sized YAMAHA, but make up for it in reliability and tough as nails durability.

[Wolf]

Not to sound dumb, what does looper mean or stand for? I've never heard that terminology before.

[THEFERMANATOR]

Originally Posted by Wolf

Not to sound dumb, what does looper mean or stand for? I've never heard that terminology before.

Looper refers to a 2 stroke engine using a loop charged style porting whereas older 2 strokes and some smaller models until recently used cross-flow porting. Cross flow engines use a tall dome on the top of the piston crown to direct the incoming air into the combustion chamber and push the exhaust out. Loop charged engines use a flat top piston or a small crown on the piston as the ports direct the airflow in and use that flow of air to direct teh exhaust out. Cross flow engines are much more efficient at lower RPM's, but use more fuel at higher RPM's due to the porting designs short falls. Loop charged engines don't idle as well since the porting uses airflow to direct the gases through the combustion chamber. When RPM's are low the airflow is low which makes the porting less efficient, but when you increase the RPM's and up the airflow the loop charged porting comes into its range and increases efficiency which allows them to make more power up high with better fuel efficiency.

Some reading for you if your interested.
http://en.wikipedia.org/wiki/Two-stroke_engine

[phester]

Originally Posted by THEFERMANATOR

The silver star series I believe was just a bass boat designation, pretty much just decals. The 60 degree looper engines are argueably the best outboard that OMC EVER built. They are a bit thirstier than an equivelant sized YAMAHA, but make up for it in reliability and tough as nails durability.

Thanks for the input Ferm. It has been a great motor the five years that I have had it. It has only let me down once due to ethanol rotting away the diaphram in the fuel pump. Outside of that , she hasn't skipped a beat.

[Destroyer]

Originally Posted by fishnfetch

I'm spinning a 14 1/2x17 aluminum prop, i may try and tinker with that as well but i need to be able to measure fuel flow before i do

By all means do so. That engine can easily spin a 21p alum prop. I run a 19p SS prop and it does just fine. Truthfully I think I get better fuel economy with the higher pitch. There's plenty of horses available to spin it, so why not use them?

[fishnfetch]

i do have a 14.5x19 aluminium that came with the boat. the previous owner said the engine would only spin 5500 rpm or so whereas the 17p spins 5800 rpm or so. i dont think he really knew anything about over propping, he just wasnt that knowledgeable about boats. he just liked the rpm i think. what effect do you think the 19p would have versus the 17p on my performance and economy?